Kendra Pierre-Louis: For Scientific AmericanIt is Science quicklymy name is Kendra Pierre-Louis, I’m replacing Rachel Feltman.
At the end of 2024, Nicola Coughlan, the actress famous for her work on Girls of Derry And The Bridgerton Chronicles, was asked about working with Ncuti Gatwa, who played the 15th Doctor in Doctor Who. His response was, “It looks amazing and it smells amazing.” »
Listen, I understand. A person’s scent, whether good or bad, can leave a lasting impression. That’s why we invest so much money in scented bath products, deodorants and perfumes.
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But beneath all these products lies our natural fragrance. And while factors like illness and how often we bathe can affect that smell, so can food, according to a number of studies.
Independent science journalist Sofia Quaglia covered this research, and we spoke to her about the surprising ways what we eat can affect how we smell. Here is that conversation.
Thank you very much for being with us today. So if I eat a lot of candy I’ll start to smell good? [Laughs.]
Sofia Quaglia: [Laughs.] I don’t think… no, it’s not that clear. So obviously this is a very new area and we are only starting to collect data. We don’t have a lot of data that we can really draw really good lines on, like “Smelling sweet is because you ate sweet things” or “Smelling sour is because you ate sweet and sour things.”
And in general, it’s not really a simple process, is it, because the food passes through our body and is digested in our gut. And then either we smell because our breath smells a certain way because of the volatile chemicals that come up from our intestines, or because they’ve passed through our bloodstream and we’re expelling them, right? So sugars, foods, and delicious sweets go through many processes before affecting our smell. [Laughs.]
Pierre-Louis: One of the things I found surprising in your article is the work researchers have done on how garlic causes body odor. Can you talk about this work?
Quail: Yeah, I love it. So obviously, we all love to eat garlic; It makes things super tasty. But our breath no longer smells as delicious afterward. [Laughs.] I know a lot of people wouldn’t enjoy a kiss with garlic-smelling breath. And so the researchers – that’s one of the reasons they targeted him, right? They say, “Oh, it’s the most annoying smell when you smell it on someone’s breath. Let’s see what happens to body smell after garlic,” right?
So the researchers had about 40 men wear underarm pads – like absorbent armpit pads – to collect their sweat for about 12 hours. And then they made some of them eat a little garlic, some of them a lot of garlic, and some of them, garlic supplements.
Then they had [about] 80 women rated the scent of these pads, which is pretty gross if you think about it too much. [Laughs.]
Pierre-Louis: Yeah, how do I sign up for this study? [Laughs.]
Quail: I didn’t do it. I didn’t sign up for this.
And then women basically had to rate men’s smell, based on, for example, subjective evaluations of how they felt, whether they were pleasant and attractive or masculine and intense. So they filled out a survey.
And the results suggest that men consuming a little garlic didn’t make these women react in any particular way, but those who ate a lot of garlic were perceived as very sexy, so their sex appeal rankings increased. So the smell of garlic under the armpit smelled good [Laughs]it smelled delicious, it smelled sexy.
To the researchers themselves, I spoke to them when… after they had conducted the study. They were also quite confused. They were like, “We had to do this three times because we didn’t think the data made sense,” right? You would also expect garlic to smell bad under the armpits. So they were also confused and surprised, and they thought it was quite amusing to have this data.
And actually, they thought about it a lot, and their theory right now is that, you know, maybe – because garlic is a good health food, right? It is a healthy food. It contains a lot of antioxidants. It has many antimicrobial properties that improve people’s health. Maybe it’s what makes someone unconsciously sexier. It’s because, you know, we’ve evolved to select romantic or sexual partners who are healthy because of the way evolution works and the way our bodies are programmed to think, like, “Oh, we have to procreate.” So maybe that’s what’s happening? It is this evolutionary lens that scientists have tried to explain.
Pierre-Louis: So the solution is this: eat a diet rich in garlic, but really make sure you brush your teeth.
Quail: Exactly. Brush your teeth, then go around your armpits, like…
Pierre-Louis: [Laughs.]
Quail: Musty. [Laughs.]
Pierre-Louis: You can’t see Sofia [Laughs]but she raises her arms, to show us her armpits.
But the garlic research sort of aligns with broader research that suggests eating lots of fruits and vegetables tends to make us feel better, at least from a sweating standpoint. This may be the case, depending on your gas levels as a human, it could be hit or miss with your GI tract and breathing. But when it comes to sweating in particular, it seems like lots of fruits and lots of vegetables are pretty good for us.
Quail: Yeah, so while our pee might smell a little funny after eating asparagus or we might get a little gas after some vegetables, similar studies in which people wore anti-sweat pads and other things – I think this one was done in Australia – found that men who ate more fruits and vegetables smelled better. They smelled fruitier, more floral, sweeter and more broadly, yes, fruits and vegetables made them more attractive to women who smelled their perfume.
And again, the researchers justify that by saying, “Okay, well, it’s probably because, you know, vegetables, fruits, they’re healthy for our diet, they make our body healthy and strong, and maybe that’s what our body scent then communicates unconsciously.”
But again, these are very small studies with small sample sizes, so we don’t have, like, charges of data. But overall, there seems to be a trend or pattern here.
Pierre-Louis: Are there foods or things we eat that can make us less attractive, for example, smell worse?
Quail: Although there isn’t a lot of data and we’re just starting to see emerging trends, researchers have started to see some trends in things that make us feel a little less pleasant. So for example, [some of] the same team that put the absorbent pads for garlic [Laughs]they also looked at whether meat makes us more attractive.
They had men eat a lot of meat or a meat-free diet for two weeks, then, again, had women rate their scents for pleasantness, attractiveness, masculinity and intensity. And the smell of men who didn’t eat meat was, on average, rated as more attractive, more pleasant, and less intense.
And again, the researchers had to scratch their heads about this because they were like, “Oh, but what… I mean, we, throughout evolution, we’ve always eaten meat. Why would that make us smell less pleasant?” This was not what they expected, as meat is considered an important part of the human diet.
But researchers also knew, you know, that early humans ate meat, sure, but they ate a lot less meat than we eat today, and they didn’t eat the super, ultra-processed meat that we eat now. They ate different types of meat. They ate game. Maybe that’s the kind of effect we’re seeing there.
And another is alcohol. Although alcohol can relax us and put us in a better mood, it seems to be one of those that doesn’t smell so good.
Pierre-Louis: I feel like, with alcohol in particular, we know this intuitively. If someone, you know, went to college and drank a lot [Laughs]there is a smell that comes out after a hard night of drinking that is not great. But the meat was This is a bit surprising, especially now, in a time when so many people advocate meat-only diets. We have the impression [Laughs]in addition to the health effects that can come from eating only meat, it can also make you less attractive to the people you would like to attract.
Quail: [Laughs.] Yeah, again, this is very early data, early days…
Pierre-Louis: RIGHT.
Quail: These are very small studies, so I don’t know if we can really make any huge, sweeping statements, but there seems to be a small, subtle change, so depending on how important you think your smell is. [Laughs]this might be something to consider.
I think an important caveat to point out here is that a lot of this is also culturally mediated. Things that someone who grew up in a certain type of culture might not find appealing in terms of scent, but someone from another culture might. So we have to take all of this into consideration and see that there are obviously subjective preferences; there are cultural preferences. If you grew up eating rice and curry your whole life, you’ll obviously have a different predisposition to that flavor, compared to someone who’s never had rice and curry before, right?
So there’s a lot of cultural mediation that we need to think about, and there’s a lot of context. That’s why it’s been pretty difficult to set up these experiments, right, aside from the gross parts of, like, how can we collect men’s sweat from their armpits? [Laughs.] So I think it’s an extremely fascinating area of study, for sure.
Pierre-Louis: But we also know that scent is important intuitively. For example, everyone talks about the smell of a newborn or, you know, your partner’s old hoodie because it always smells like him when he’s away from you. So we know we sort of, yes, it’s culturally mediated, but there seems to be an element there in the sense that, for example, the way a person smells can really determine whether you’re attracted to them or whether you’re repelled by them.
Quail: Of course, and what’s super fascinating here is that each of us has a unique scent profile, right, like a fingerprint. There’s a growing body of research here that shows that everything from our personality type, like whether you’re extroverted or introverted, to our mood and our health, really affects how we smell, you know?
It comes from genes. It comes from hormones. This comes from health, hygiene. It comes from whether you are male or female, young or old, gay or straight, dominant or subordinate, ovulating, pregnant, sick, happy, sad. So all of these things affect how we smell and how we smell and how our body smells.
So diet is just one of the little things that adds to that, right? This is also why it’s hard to say, “Okay, I’m going to make decisions about my smell based solely on my diet from now on,” because [Laughs] there are many more There are things at stake, that’s for sure.
Pierre-Louis: No, sorry, what I heard is that from now on I’m going to live solely on a diet of broccoli and carrots, with apples: broccoli, carrots and apples. [Laughs.]
Quail: And jelly beans. Don’t forget the candy.
Pierre-Louis: I can’t forget the candy.
Pierre-Louis: That’s all for today. Tune in Friday, when we’ll talk about people who have made incredible scientific contributions that have been lost or hidden over time.
But before we go, we’d like to ask for your help with an upcoming episode: it’s about kisses. Tell us about your most memorable kiss. What made him special? How did you feel? Record a voice memo on your phone or computer and send it to ScienceQuickly@sciam.com. Be sure to include your name and where you are from.
Science quickly is produced by me, Kendra Pierre-Louis, with Fonda Mwangi, Sushmita Pathak and Jeff DelViscio. This episode was edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more recent and in-depth scientific news.
For Scientific American, This is Kendra Pierre-Louis. Have a good week!
